The Emissivity of Transition Metals in the Infrared

1965 ◽  
Vol 87 (2) ◽  
pp. 173-176 ◽  
Author(s):  
R. A. Seban
Keyword(s):  
Electrical Conductivity ◽  
High Temperature ◽  
Transition Metals ◽  
Temperature Rise ◽  
Room Temperature ◽  
Charge Carriers ◽  
Iron Nickel

Absorptivities of iron, nickel, and platinum are presented for room temperature and emissivities for temperatures of the order of 2000 deg R for wavelengths from 1 to 15 microns. These are compared to the predictions made from Roberts’ theory for absorption by two sets of charge carriers, using the parameters that he deduced, and favorable correspondence is achieved with the absorptivity of iron and of nickel at room temperature. Following his postulate that all of the change in electrical conductivity that is consequent to the temperature rise occurs in the more important set of carriers, adequate predictions of the emissivity at high temperature are obtained as well.

scholarly journals The Phase Transition and Dehydration in Epsomite under High Temperature and High Pressure

Crystals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 75 ◽  
Author(s):  
Linfei Yang ◽  
Lidong Dai ◽  
Heping Li ◽  
Haiying Hu ◽  
Meiling Hong ◽  
...  
Keyword(s):  
Phase Transition ◽  
Electrical Conductivity ◽  
High Pressure ◽  
High Temperature ◽  
Magnesium Sulfate ◽  
Room Temperature ◽  
Diamond Anvil Cell ◽  
Vibrational Modes ◽  
Diamond Anvil ◽  
T Phase

The phase stability of epsomite under a high temperature and high pressure were explored through Raman spectroscopy and electrical conductivity measurements in a diamond anvil cell up to ~623 K and ~12.8 GPa. Our results verified that the epsomite underwent a pressure-induced phase transition at ~5.1 GPa and room temperature, which was well characterized by the change in the pressure dependence of Raman vibrational modes and electrical conductivity. The dehydration process of the epsomite under high pressure was monitored by the variation in the sulfate tetrahedra and hydroxyl modes. At a representative pressure point of ~1.3 GPa, it was found the epsomite (MgSO4·7H2O) started to dehydrate at ~343 K, by forming hexahydrite (MgSO4·6H2O), and then further transformed into magnesium sulfate trihydrate (MgSO4·3H2O) and anhydrous magnesium sulfate (MgSO4) at higher temperatures of 373 and 473 K, respectively. Furthermore, the established P-T phase diagram revealed a positive relationship between the dehydration temperature and the pressure for epsomite.

The Potential of Electronic High Temperature Devices Based Upon Polymer Derived Ceramics

2005 ◽  
Author(s):  
Weixing Xu ◽  
Jayanta Kapat ◽  
Louis C. Chow ◽  
Linan An ◽  
Wenge Zhang
Keyword(s):  
Electrical Conductivity ◽  
High Temperature ◽  
Room Temperature ◽  
Polymer Derived Ceramics ◽  
Micro Parts ◽  
Varied Composition ◽  
Potential Use ◽  
Lithography Technique ◽  
High Temperature Gas ◽  
Good Agreement

In this paper, we describe the potential use of polymer-derived ceramics (PDCs) for micro-sensors for high-temperature gas turbine applications. PDCs have several unique properties such as ease of microfabrication, excellent mechanical, materials and thermal properties, and tunable electrical conductivity. The electrical conductivity of PDCs with varied composition is measured as a function of temperature from room temperature upon to 700°C. Our results reveal that with suitable doping, the electrical conductivity could be controlled from insulating to semiconducting. Next, we measure the cure depth of the precursors as a function of UV intensity and exposure time. A model is developed to predict the cure depth as a function of photoinitiator concentration and light intensity. Good agreement between theory and experimental data is obtained. Finally, a few typical micro parts are fabricated by lithography technique.

ARSENIDES OF TRANSITION METALS: THE ARSENIDES OF IRON AND COBALT

1957 ◽  
Vol 35 (5) ◽  
pp. 449-457 ◽  
Author(s):  
R. D. Heyding ◽  
L. D. Calvert
Keyword(s):  
High Temperature ◽  
Transition Metals ◽  
Room Temperature ◽  
Pressure Data ◽  
Decomposition Pressure

Alloys of cobalt and arsenic containing up to 60% As by weight have been studied by means of room temperature and high temperature Debye–Scherrer diagrams. Two compounds exist at room temperature, Co2As and CoAs, both of which undergo crystallographic transformations at higher temperatures, the former between 400 °C. and 500 °C., the latter at about 950 °C. A third compound, probably Co3AS2, is formed by the reaction of Co2As with CoAs above 940 °C. The structures of these compounds are compared with the structures of the corresponding compounds in the iron/arsenic system. These results indicate the necessity of slight revisions to the Co/As diagram, and raise serious questions in respect of the validity of decomposition pressure data reported recently for cobalt arsenides.

ARSENIDES OF THE TRANSITION METALS: II. THE NICKEL ARSENIDES

1957 ◽  
Vol 35 (10) ◽  
pp. 1205-1215 ◽  
Author(s):  
R. D. Heyding ◽  
L. D. Calvert
Keyword(s):  
High Temperature ◽  
Melting Point ◽  
Transition Metals ◽  
Stability Region ◽  
Room Temperature ◽  
Metastable Phase ◽  
The Other ◽  
Incongruent Melting ◽  
Diffraction Patterns ◽  
The Stability

Alloys of nickel and arsenic containing up to 60% As by weight have been studied by means of room temperature and high temperature Debye-Scherrer diagrams. Three compounds have been identified: Ni5As2, Ni12−xAs8 (maucherite), and NiAs (niccolite). The first of these is homogeneous from Ni5As2 to Ni4.8A2 at room temperature, and to Ni4.6As2 above 250 °C., while the latter is homogeneous from NiAs to Ni0.95As. Contrary to expectations the stability region of the compound Ni12−xAs8 is very narrow, and occurs at Ni11As8 rather than at Ni3As2. Evidence is presented in support of Hansen's contention that this compound has an incongruent melting point. Alloys in the region corresponding to Ni4.6As2 undergo two transitions below 200 °C, one of which is martensitic and produces a metastable phase, while the other is believed to result in the formation of a new compound, as yet unidentified. The diffraction patterns are discussed in some detail.

Structural transitions and electrical conductivity of C60 films at high temperature

1996 ◽  
Vol 11 (8) ◽  
pp. 2071-2075 ◽  
Author(s):  
Jinlong Gong ◽  
Guobin Ma ◽  
Guanghua Chen
Keyword(s):  
Electrical Conductivity ◽  
High Temperature ◽  
Room Temperature ◽  
X Ray Diffraction ◽  
Energy Band Gap ◽  
Defect States ◽  
Order Of Magnitude ◽  
Fcc Phase ◽  
New Phase ◽  
C60 Films

X-ray diffraction analysis on C60 films shows that besides fcc phase, there also exists hcp phase, as well as a new crystalline phase with interplanar spacing (d-spacing) of planes parallel to the substrate 0.95 nm. The new phase may relate to the intercrystalline packed C60 molecules between fcc crystallites. The room temperature electrical conductivity of C60 films is found to be in the range of 10−5–10−8 (Ω · cm)−1. The room temperature conductivities of C60 films annealed at temperatures above 473 K are lower by one order of magnitude than those at temperatures below 463 K. This is because the interconnection between the fcc crystallites is weakened due to the disappearance of the new intercrystalline phase and the subsequent heightening of the intercrystalline potential barrier. From the measurement on the conductivity versus time when the film is maintained at a constant temperature, we identified the increase of conductivity is the result of the decrease of hcp phase, while the decrease of conductivity is due to the decrease of the new intercrystalline phase. Because the structures of the films become highly ordered, and defect states in the energy band gap decrease on annealing at high temperature, the conductivity activation energy increases.

scholarly journals Кристаллофизическая модель электропереноса в суперионном проводнике Pb-=SUB=-1-x-=/SUB=-Sc-=SUB=-x-=/SUB=-F-=SUB=-2+x-=/SUB=- (x=0.1)

2018 ◽  
Vol 60 (4) ◽  
pp. 710
Author(s):  
Н.И. Сорокин
Keyword(s):  
Electrical Conductivity ◽  
Ionic Conductivity ◽  
Single Crystals ◽  
Room Temperature ◽  
Charge Carriers ◽  
Bulk Conductivity ◽  
Characteristic Parameters ◽  
Calculated Concentration ◽  
Fluorite Type ◽  
Mobile Ions

AbstractThe frequency (ν = 10^–1–107 Hz) dependences of electrical conductivity σ(ν) of single crystals of superionic conductor Pb_0.9Sc_0.1F_2.1 (10 mol % ScF_3) with fluorite type structure (CaF_2) in the temperature range 153–410 K have been investigated. The static bulk conductivity σ_ dc =1.5 × 10^–4 S/cm and average hopping frequency ν_ h = 1.5 × 10^7 Hz of charge carriers (mobile ions F^−) at room temperature (293 K) have been defined from the σ_ dc (ν) experimental curves. Enthalpies of thermoactivated processes of ionic conductivity σ_ dc ( T ) (Δ H _σ = 0.393 ± 0.005 eV) and dielectric relaxation ν_ h ( T ) (Δ H _h = 0.37 ± 0.03 eV) coincide within their errors. A crystal-physical model of fluorine-ion transport in a Pb_0.9Sc_0.1F_2.1 crystal lattice has been proposed. The characteristic parameters of charge carriers have been calculated: concentration n _mob = 2.0 × 10^21 cm^−3, the distance of the hopping d ≈ 0.5 nm and mobility μ_mob = 4.5 × 10^−7 cm^2/s V (293 K).

Phase Behavior of La1-xMnO3-1.5x with Trivalent Manganese Ion

2004 ◽  
Vol 449-452 ◽  
pp. 741-744 ◽  
Author(s):  
M. Kobayashi ◽  
Hirohisa Sato ◽  
Naoki Kamegashira
Keyword(s):  
Phase Transition ◽  
Thermal Analysis ◽  
Electrical Conductivity ◽  
High Temperature ◽  
Thermal Diffusivity ◽  
Room Temperature ◽  
Orthorhombic Phase ◽  
Ceramic Method ◽  
X Ray ◽  
Manganese Ion

Defect perovskite, La1-xMnO3-1.5x (x=0.00-0.10), was synthesized by conventional ceramic method and phase transition was measured by X-ray diffractometry, electrical conductivity, thermal diffusivity and thermal analysis. La1-xMnO3-1.5x (x=0.00-0.09) have single orthorhombic phase corresponding to GdFeO3 type perovskite structure at room temperature, while have rhombohedral structural at high temperature. The transition temperatures observed from electric conductivity, DSC, thermal diffusivity were mostly in agreement and they slightly decrease with increasing x.

Variations in the photoconductivity and in the electrical counting properties of diamonds

1956 ◽  
Vol 234 (1198) ◽  
pp. 419-432 ◽  
Keyword(s):  
Electrical Conductivity ◽  
Electric Field ◽  
Hall Effect ◽  
Temperature Effects ◽  
Room Temperature ◽  
Red Light ◽  
Quantitative Relationship ◽  
Charge Carriers ◽  
Light Irradiation ◽  
Hall Effect Measurements

The electrical conductivity produced by β -ray bombardment and by light irradiation in several diamonds was investigated in the temperature range 150 to 500° K. Considerable uniformity was observed in the behaviour of the specimens; all of them polarized strongly in the dark at room temperature, and polarization could be effectively eliminated by pulsing the electric field while maintaining the β -flux. Both the counting response and the photoconductivity increased as the temperature was lowered. This was interpreted as being largely due to an increase in the mobility of the charge carriers at lower temperatures, the quantitative relationship being consistent with Hall effect measurements. Accumulation of polarization was reduced by irradiation with red light or by elevation of temperature; at 420° K little sign of polarization remained. From various temperature effects, the thermal depths of the trapping levels in these diamonds were estimated at 0⋅6, 0⋅8 and 1 eV.

Synthesis and Electrical Properties of Mo-ZrO2 Cermet

2011 ◽  
Vol 311-313 ◽  
pp. 2121-2126
Author(s):  
Ji Fang Xu ◽  
Gong Yuan Liu ◽  
Lei Tang ◽  
Jie Yu Zhang ◽  
Chang Jie
Keyword(s):  
Electrical Conductivity ◽  
High Temperature ◽  
Electrical Properties ◽  
Room Temperature ◽  
Optical Microscope ◽  
Metal Phase ◽  
Phase Zone ◽  
Ceramic Phase ◽  
Mo Content ◽  
Increasing Temperature

Under the protected condition of the purified argon atmosphere, Mo-ZrO2cermets were sintered by Mo powder and ZrO2powder at 1873K for 2 hours. Mircostructure of cermets were observed by means of XRD, optical microscope and SEM anslysis. Electrical properties of sintered samples with different Mo content and temperature were measured using DC four-electrode method. The results showed that metal phase and ceramic phase were independent of each other. With the reduction of Mo content, Mo metal phase as the continuous network structure is dispersedly distributed in the ceramic phase zone. The electrical conductivity of cermets at room temperature increased with decreaseing of the Mo content. The trend that the high-temperature electrical conductivity of cermets changed with the Mo content is the same as the trend that at the room temperature. When the Mo content is greater than 40%, the high-temperature electrical conductivity increased linearly with increasing temperature. The electrical conductivity of 40mol-% Mo-ZrO2reached the peak at 1223K and 1473K.

High Electrical Conductivity in Organic Single-Component Systems Based on 2,5-Dimethylthio-TCNQ

1993 ◽  
Vol 328 ◽  
Author(s):  
J. S. Zambounis ◽  
J. Mizuguchi ◽  
H. Hediger ◽  
J. Pfeiffer ◽  
B. Schmidhalter ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Electrical Properties ◽  
Room Temperature ◽  
Single Component ◽  
Charge Carriers ◽  
Optical And Electrical Properties ◽  
High Electrical Conductivity ◽  
Component System ◽  
Component Systems ◽  
Neighboring Molecule

ABSTRACT2,5-dimethylthio-TCNQ has been newly synthesized, and its optical and electrical properties have been investigated in evaporated films. A high electrical conductivity of σ=2× 10−5 Scm−l has been measured at room temperature. The present single-component system is found to contain 2×1017 spins/cm3. The charge carriers are presumably due to incorporated impurities which give the ESR signals. Carrier hopping is considerably facilitated by close intermolecular S-N contacts between the S atom of the -SCH3 group of one molecule and the N atom of -C≡N group of the neighboring Molecule.

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